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UCRL-AR-10191-19-4LLNL Site 300 Compliance Monitoring Program for the Closed Pit 1 LandfillFourth Quarter Report for 2019Figure 2. Location of the closed Pit 1 landfill at LLNL Site 300.Pit 1 is located in the Elk Ravine drainage area about 300 meters (m) or 984 feet (ft) above meansea level (MSL). Groundwater generally flows in an east-northeast direction beneath Pit 1 (Figure3), following the inclination (dip) of underlying Miocene-age sedimentary rocks (WebsterScholten, 1994).The current monitoring network at Pit 1 consists of twelve monitoring wells. These include eightdetection monitoring wells and four evaluation monitoring wells (Figure 3). The detectionmonitoring wells used to sample the ground water in the vicinity of Pit 1 include: wells K1-01Cand K1-07 located hydrologically upgradient from Pit 1; down-gradient wells K1-02B, K1-04, K105, and W-PIT1-2326; and cross-gradient wells K1-08 and K1-09. The primary purpose of thedetection monitoring wells is to detect any new release of COCs to groundwater. COCs, as definedby Title 23 of the California Code of Regulations (CCR), Chapter 15, are waste constituents,reaction products, and hazardous constituents that are reasonably expected to be in or derived fromwaste buried in the Pit 1 Landfill. LLNL collects, analyzes, and statistically evaluates one samplequarterly from each detection monitoring well.The evaluation monitoring wells are all downgradient of the Pit 1 detection wells and include K106, W-PIT1-2620, W-PIT1-2209, and W-865-2005, as required by the Monitoring ReportingProgram (MRP). Well W-PIT1-02 is no longer sampled because it was abandoned and replacedby well W-PIT1-2620 during the third quarter of 2011 due to well damage. These evaluationmonitoring wells were added to the Pit 1 monitoring and reporting requirements to track existingplumes of perchlorate and tritium from up-gradient sources. LLNL collects and analyzes oneESH-EFA-WQ-20-17014– CQ/AC:mgp2

UCRL-AR-10191-19-4LLNL Site 300 Compliance Monitoring Program for the Closed Pit 1 LandfillFourth Quarter Report for 2019sample quarterly from each evaluation monitoring well and annually conducts trend analyses oftritium and perchlorate concentrations.All the wells are screened in the uppermost water-bearing zone (hydrostratigraphic unit or HSU),which occurs in the Neroly Formation lower blue sandstone (Tnbs1/Tnbs0) HSU. The NerolyFormation contains the main aquifer beneath Site 300. Pit 2, which was closed before RCRA wasenacted, is hydrologically upgradient of Pit 1. In 1992, a 2.4 m (8 ft) thick RCRA cap containingan impermeable layer of clay that is 0.6 m (2 ft) thick was constructed over Pit 1. The cap preventsrainwater from percolating through the waste buried in the pit. A water diversion channel wasconstructed around the pit cap to divert storm water runoff away from the landfill. The diversionchannel empties into the adjacent arroyo, which in turns conveys flow towards Elk Ravine.Figure 3. Locations of Pit 1 detection and compliance monitoring wells.ESH-EFA-WQ-20-17014– CQ/AC:mgp3

UCRL-AR-10191-19-4LLNL Site 300 Compliance Monitoring Program for the Closed Pit 1 LandfillFourth Quarter Report for 2019Compliance Monitoring Program OverviewThis report fulfills quarterly requirements set forth in the following two sets of documents: (1)Waste Discharge Requirements (WDR) Order 93-100 and the February 18, 2010, MRP No. 93100, administered by the California CVRWQCB (CVRWQCB 1993 and 2010) and (2) LLNL Site300 RCRA Closure and Post-Closure Plans (PCPs), Landfill Pits 1 and 7 (Rogers/PacificCorporation 1990). The PCP was approved by the California Department of Health Services (nowthe California Department of Toxic Substances Control). The combined requirements includequarterly groundwater sampling and analyses to detect potential releases of COCs from the landfill,annual and post-major storm event visual inspections of pit cap integrity, repairs as necessary tomaintain the integrity of the landfill and its water-diversion system, annual elevationmeasurements of cap survey markers to detect subsidence, an annual inspection of the cap by anindependent engineer, and these quarterly written monitoring reports. The fourth quarter Pit 1report provides statistical limits and graphs of groundwater measurements (Chan, 2018).Quality AssuranceTo ensure quality data, LLNL works within the established Quality Assurance (QA) program ofthe LLNL Environment, Safety & Health Directorate. LLNL uses protocols and procedures thatcover all aspects of groundwater sampling, sample tracking, and data management. These writtenprotocols and procedures are contained in the LLNL Livermore Site and Site 300 EnvironmentalRestoration Project Standard Operating Procedures (SOPs) (Goodrich and Lorega, 2016), and theEnvironmental Monitoring Plan (Brunckhorst, 2019). SOPs are used to minimize inadvertentsample contamination and maintain sample integrity from the well to the analytical laboratory Datamanagement SOPs ensure that all laboratory measurements are received, accurately recorded, andproperly stored both in a computer database and in hardcopy format.Each quarter, a duplicate (collocated) set of groundwater samples is collected from eachmonitoring network and a set of blank samples is prepared from a randomly chosen well. Inaddition, equipment blanks are prepared and analyzed to ensure that sampling equipment isproperly cleaned before use. Each day, when samples are collected for volatile organic compound(VOC) analysis, a trip blank (prepared at the analytical laboratory) is carried into the field. It isreturned unopened to the analytical laboratory for VOC analysis. If VOCs are detected in a tripblank and in any of the routine samples obtained that day, sample results may be discounted, andnew sampling may be performed.As required by Executive Order 12770, measurements are reported in Système Internationale (SI)units. The SI unit for radioactivity is the becquerel (Bq), equal to 1 nuclear disintegration persecond. The more commonly used unit, picocurie (pCi), is equal to 1 nuclear disintegration per 27seconds. As a convenience, maximum contaminant levels (MCLs) for radioactivity in drinkingwater are given in both becquerels per liter (Bq/L) and picocuries per liter (pCi/L) in Table 1.Note that MCLs are provided for reference only, because this report does not involve wells usedfor potable domestic, livestock, or industrial water supply.ESH-EFA-WQ-20-17014– CQ/AC:mgp4

UCRL-AR-10191-19-4LLNL Site 300 Compliance Monitoring Program for the Closed Pit 1 LandfillFourth Quarter Report for 2019Table 1. MCLs for radioactivity in drinking water.Radiological parameterGross alphaGross betaTritiumRadium (total)Uranium (total)MCL (Bq/L)0.5551.857400.1850.74MCL (pCi/L)155020,000520Description of Report ContentsThe “Summary of Analytical Results” section summarizes any COC concentrations detected ingroundwater samples from detection monitor wells during the fourth quarter of 2019. COCmeasurements that exceeded SLs or MCLs in drinking water are also discussed in this report.Appendix A Tables A-1, A-2, and A-3 contain the groundwater analytical measurements for Pit1 for the fourth quarter of 2019. Table A-4 shows the sample dates and A-5 shows the reportinglimits (RLs) for the Pit 1 VOC COCs. In Tables A-1 through A-3, results that are less than theRL are prefaced with a less than sign ( ). Note that the Appendix A tables may include somesmall negative values for radioactivity measurements. These are below the method RLs and arecalculated values. They simply indicate that the radioactivity for that groundwater sample is lessthan a low activity reference standard. Appendix A also contains a groundwater elevation contourmap (Figure A-1) for the Tnbs1/Tnbs0 HSU at Pit 1. This map is only presented in the second andfourth quarter compliance monitoring program reports.Appendix B explains the methods used to determine the SL for a COC at a monitoring well.Requirements for statistical treatment of groundwater data are established in the CCR, Title 23,Division 3, Chapter 15, Section 2550.7. LLNL uses a statistical prediction limit method toimplement intrawell comparisons. The method uses the average and standard deviation ofhistorical measurements to calculate a SL value. If a routine quarterly COC measurement exceedsits SL and is confirmed by retesting, it is reported to the CVRWQCB as statistically significantevidence of a release.Appendix C contains the results for QA sample analyses performed during the fourth quarter of2019 at Pit 1 in Table C-1.Appendix D consists of Table D-1 summarizing COCs and the sampling frequencies in themonitoring network for the pit. The regulatory drivers for each constituent of concern are alsoincluded in Table D-1.Appendix E consists of Table E-1 and presents well specification and construction details fordetection monitoring and evaluation monitoring wells.Appendix F contains hydrographs for all compliance monitoring wells.ESH-EFA-WQ-20-17014– CQ/AC:mgp5

UCRL-AR-10191-19-4LLNL Site 300 Compliance Monitoring Program for the Closed Pit 1 LandfillFourth Quarter Report for 2019Appendix G contains field logs for all compliance monitoring wells.Appendix H consists of the statistical limits and graphs of groundwater measurements.Summary of Analytical ResultsThis section summarizes the analytical results for Pit 1 for the fourth quarter of 2019 and reportson the requirements of the CVRWQCB Pit 1 MRP and post-closure plan requirements. During thefourth quarter monitoring period, no new releases of COCs to groundwater from the pit are evidentin the data. As part of the MRP, SLs used to monitor groundwater COCs are shown on Table A1. The MRP requires that two confirmation samples be collected from wells where COCs exceedSLs. If either of the two confirmation sample concentrations exceeds the SL, a finding ofstatistically significant evidence of a release is confirmed and a seven-day notification letter mustbe submitted to the CVRWQCB. The statistical tests used to evaluate these data are identified inAppendix B.Detection Monitoring WellsAnalytical results indicate that there were three COCs (beryllium, cadmium, and uranium) detectedin routine samples above their respective SLs from the Pit 1 wells and one COC (zinc) detected ina duplicate sample above the SL. The presence of these COCs does not indicate an actual releasefrom Pit 1 and details of these SL exceedances are explained below. No other COCs exceeded anSL this quarter and no COCs exceeded an MCL.Several statistical limit exceedances occurred at cross-gradient well K1-09 during the fourthquarter for the following constituents of concern – beryllium, cadmium, and zinc (in the duplicatesample). Sampling performed on November 4th yielded a beryllium concentration of 1.2 µg/L (SL 0.5 ug/L), cadmium concentration of 1 ug/L (SL 0.5 ug/L), and zinc concentration of 21 µg/L(SL 20 µg/L) in the duplicate sample. Email correspondence was made to Aimee Phiri onJanuary 6th noting the SL exceedance and the collection of two retest samples for the COCs.Beryllium and cadmium had not been previously detected in samples from well K1-09 since 2007,when sampling and analysis for beryllium and cadmium were first conducted. In the duplicatesample for zinc, a SL exceedance was observed, and two retest samples were requested. Zinc waslast detected at 36 µg/L in the first quarter of 2019. LLNL will evaluate the beryllium, cadmium,and zinc concentrations from this well when the retest sample results are available, and reportresults in the next quarterly report or in a 7-Day letter.Sampling performed on December 17th at down-gradient well W-PIT1-2326 yielded total uraniumactivities of 0.146 Bq/L and 0.179 Bq/L (SL 0.139 Bq/L) in the routine and duplicate samplerespectively. The total uranium activities in this wells and other Pit 1 wells have been discussedin past reports (Blake, 2011; Blake, 2015, Chan, 2019) and in letters to the CVRWQCB (Schultz,2010 [90-Day Letter]; Pierce, 2011 [Seven-Day Written Notification]). As stated in these lettersand reports, the analyses and information that LLNL has provided to the CVRWQCB indicate thatthe total uranium activities in the Pit 1 wells have historically been within background ranges.Moreover, the mass spectrometric uranium isotope analysis of a fourth quarter 2018 sample fromESH-EFA-WQ-20-17014– CQ/AC:mgp6

UCRL-AR-10191-19-4LLNL Site 300 Compliance Monitoring Program for the Closed Pit 1 LandfillFourth Quarter Report for 2019well W-PIT1-2326 yielded a 235U/238U atom ratio of 0.00728, within the natural range near 0.0072.Thus, the SL exceedances of total uranium in Pit 1 well samples do not indicate actual evidence ofa release of total uranium from the pit, but rather reflect background variability in total uranium inground water within a volcaniclastic aquifer. Two retests for total uranium from this quarter wererequested and the results will be evaluated in a 7-day letter or in the next quarterly report.In addition to the normal reporting for detection monitoring wells with COCs and correspondingSLs, this report evaluates additional constituents that have shown elevated concentrations and aremonitored under the PCP or under LLNL’s surveillance monitoring program per DOE Order458.1. The concentrations of selected VOCs detected in groundwater samples from detectionmonitoring wells are summarized and presented as total VOCs (Table A-2). VOCs were detectedin groundwater samples from upgradient well K1-07 (0.92 µg/L) and cross-gradient wells K1-08(25 µg/L) and K1-09 (42g/L). Total VOC concentrations are similar to those reported last quarter.The only VOC observed in these samples was Freon-113. The Freon-113 arises from a source atBuilding 865, about 300 m (984 ft) northwest of Pit 1 (Taffet et al., 2019b). The Freon-113concentrations for ground water samples collected from wells K1-05, K1-08, and K1-09 are plottedon Figure 4, below. The Freon-113 concentration trends for these detection monitoring wells havebeen relatively similar and have each varied within narrow ranges since 2002. The maximumconcentrations of Freon-113 measured in these detection monitoring wells are well below the 1,200µg/L MCL.Figure 4. Freon-113 concentrations in groundwater samples from detection monitoring wells at Pit 1.ESH-EFA-WQ-20-17014– CQ/AC:mgp7

UCRL-AR-10191-19-4LLNL Site 300 Compliance Monitoring Program for the Closed Pit 1 LandfillFourth Quarter Report for 2019Evaluation Monitoring WellsEvaluation monitoring wells are required by the MRP and analytical results for samples from thesewells are tabulated in Table A-3. The table lists physical parameters as well as perchlorate andtritium analytical data. These wells are used to track the existing plumes of perchlorate and tritiumfrom an up-gradient source. As required by the MRP, annual time-series plots of perchlorate andtritium concentrations in evaluation monitoring wells are presented in each fourth quarter/annualreport.Of the four current evaluation monitoring wells (W-PIT1-2209, W-865-2005, K1-06, and W-PIT12620), one well, K1-06, has not been sampled since 2018 due to a non-working pump. However,the well is scheduled to receive a new pump in the coming months. The fourth quarter 2019 samplefrom one of the evaluation monitoring wells, W-PIT1-2620, yielded 6.2 µg/L of perchlorate,similar to concentrations reported in previous quarterly reports. This is the only evaluationmonitoring well that yielded a detection of perchlorate this quarter, exceeding the 6 µg/L MCL forperchlorate. LLNL will continue to monitor the perchlorate concentrations in the evaluationmonitoring wells. Perchlorate concentrations in ground water samples collected from the currentevaluation monitoring wells and W-PIT1-02 (replaced.by W-PIT1-2620) since 2005 are plottedon Figure 5, below.Figure 5. Perchlorate concentrations in groundwater samples from evaluation monitoring wells atPit 1.ESH-EFA-WQ-20-17014– CQ/AC:mgp8

UCRL-AR-10191-19-4LLNL Site 300 Compliance Monitoring Program for the Closed Pit 1 LandfillFourth Quarter Report for 2019The tritium activities in fourth quarter 2019 samples from the evaluation monitoring wells wereall consistent with recent d

The current monitoring network at Pit 1 consists of twelve monitoring wells. These include eight detection monitoring wells and four evaluation monitoring wells Figure 3). The detection (monitoring wells used to sample the groundwater in the vicinity of Pit 1 include: wells K1 -01C